Audience measurement systems may be used to identify content output by a media presentation device. For example, a metering device can be equipped with microphone(s) to identify program content emanating from a media presentation device, such as a television (TV). An audio signal captured by the microphone(s) is processed either to extract an embedded watermark from the audio signal or convert the audio signal to a signature for matching against signatures stored in a reference database. Audio watermarks are embedded in media program content prior to distribution of the media program content for consumption. Reference audio signature databases are created from broadcast or distributed media program content.